The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
A typical multi-speed automatic transmission uses a combination of torque transmitting devices, such as clutches, dog clutches/synchronizers, or brakes, to achieve a plurality of forward and reverse gear or speed ratios. Selection of speed ratios is typically accomplished by a microprocessor transmission control module that employs various vehicle parameters, for example vehicle speed, and various driver input signals, for example accelerator pedal position, to select the appropriate speed ratios. The transmission then actuates or engages a combination of the toque transmitting devices to provide the desired speed ratios.
The torque-transmitting devices can use various actuating techniques and mechanisms for transferring torque from one rotating member to another. One type of torque-transmitting device uses a plurality of rotating plates and a hydraulically actuated piston. The hydraulically actuated piston is moved to an engaged position by application of a hydraulic force on the piston. However, the hydraulically actuated piston requires a regulating force to retract the piston from the engaged position. The regulating force may be provided in various manners, for example, a separate hydraulic circuit may provide another hydraulic force on the piston in order to provide the regulating force. However, hydraulic circuits may increase the size and weight of the transmission. In other applications a mechanical spring may be used to apply the regulating force to the piston. However, in previous designs the mechanical spring assembly limits the overall compact size of a transmission as typically a plurality of torque-transmitting devices are employed in each transmission. Accordingly, there is room in the art for an improved torque-transmitting device that includes a piston actuating assembly that reduces the size of the torque-transmitting device.